/*-------------------------------------------------------------------------
 *
 * scankey.c
 *      scan key support code
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      src/backend/access/common/scankey.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/skey.h"
#include "catalog/pg_collation.h"


/*
 * ScanKeyEntryInitialize
 *        Initializes a scan key entry given all the field values.
 *        The target procedure is specified by OID (but can be invalid
 *        if SK_SEARCHNULL or SK_SEARCHNOTNULL is set).
 *
 * Note: CurrentMemoryContext at call should be as long-lived as the ScanKey
 * itself, because that's what will be used for any subsidiary info attached
 * to the ScanKey's FmgrInfo record.
 */
void
ScanKeyEntryInitialize(ScanKey entry,
                       int flags,
                       AttrNumber attributeNumber,
                       StrategyNumber strategy,
                       Oid subtype,
                       Oid collation,
                       RegProcedure procedure,
                       Datum argument)
{
    entry->sk_flags = flags;
    entry->sk_attno = attributeNumber;
    entry->sk_strategy = strategy;
    entry->sk_subtype = subtype;
    entry->sk_collation = collation;
    entry->sk_argument = argument;
    if (RegProcedureIsValid(procedure))
    {
        fmgr_info(procedure, &entry->sk_func);
    }
    else
    {
        Assert(flags & (SK_SEARCHNULL | SK_SEARCHNOTNULL));
        MemSet(&entry->sk_func, 0, sizeof(entry->sk_func));
    }
}

/*
 * ScanKeyInit
 *        Shorthand version of ScanKeyEntryInitialize: flags and subtype
 *        are assumed to be zero (the usual value), and collation is defaulted.
 *
 * This is the recommended version for hardwired lookups in system catalogs.
 * It cannot handle NULL arguments, unary operators, or nondefault operators,
 * but we need none of those features for most hardwired lookups.
 *
 * We set collation to DEFAULT_COLLATION_OID always.  This is appropriate
 * for textual columns in system catalogs, and it will be ignored for
 * non-textual columns, so it's not worth trying to be more finicky.
 *
 * Note: CurrentMemoryContext at call should be as long-lived as the ScanKey
 * itself, because that's what will be used for any subsidiary info attached
 * to the ScanKey's FmgrInfo record.
 */
void
ScanKeyInit(ScanKey entry,
            AttrNumber attributeNumber,
            StrategyNumber strategy,
            RegProcedure procedure,
            Datum argument)
{
    entry->sk_flags = 0;
    entry->sk_attno = attributeNumber;
    entry->sk_strategy = strategy;
    entry->sk_subtype = InvalidOid;
    entry->sk_collation = DEFAULT_COLLATION_OID;
    entry->sk_argument = argument;
    fmgr_info(procedure, &entry->sk_func);
}

/*
 * ScanKeyEntryInitializeWithInfo
 *        Initializes a scan key entry using an already-completed FmgrInfo
 *        function lookup record.
 *
 * Note: CurrentMemoryContext at call should be as long-lived as the ScanKey
 * itself, because that's what will be used for any subsidiary info attached
 * to the ScanKey's FmgrInfo record.
 */
void
ScanKeyEntryInitializeWithInfo(ScanKey entry,
                               int flags,
                               AttrNumber attributeNumber,
                               StrategyNumber strategy,
                               Oid subtype,
                               Oid collation,
                               FmgrInfo *finfo,
                               Datum argument)
{
    entry->sk_flags = flags;
    entry->sk_attno = attributeNumber;
    entry->sk_strategy = strategy;
    entry->sk_subtype = subtype;
    entry->sk_collation = collation;
    entry->sk_argument = argument;
    fmgr_info_copy(&entry->sk_func, finfo, CurrentMemoryContext);
}
